Those are known for the receivers going bad due to them being soft and the lugs on the bolts chewing them up. Then they jam up and quit working. One solution is to send them in and get them converted to a pump which will cost anywhere from 240 bucks on up depending on where you send it too. An easier and cheaper solution which is what I did is just convert it to a straight pull action which is simple. If you take the forearm off you will see the block on the bottom of the barrel and the gas tube coming out at a 90 degree angle on the action side of that block. On the bottom of that block is a set screw and if you take that out you will see a ball bearing which I suppose is a check valve of some sort. Take the set screw out and buy a longer one about a half an inch. Take out the ball bearing and you will see the hole is smaller where the ball bearing was seated. Take a dremel tool and take down 3/4 of the longer set screw to a pencil lead thickness until it fits in that smaller hole. Leave at least 3 threads on the set screw and screw it into the hole so it blocks the gas port where it comes into the block at the 90 degree angle. This should block the gas port. IF you want to be sure you can then block the gas port tube with something if you want to just to double make sure. Though I did not and mine works fine it does not cycle the action. Use the original set screw and screw it back in behind the altered set screw. Picture the set screw with only 3 or 4 threads and a pencil lead sized shaft for the rest of it this is what you want to just fit into that smaller hole and let the threads left catch the threads in the first part of the hole and screw in.
Now what you will have is a straight pull action that will not cycle when fired (Think single shot) or take the bolt out of battery until you manually pull the bolt back with the bolt handle. This will save the receiver from getting more chewed up and now you can still shoot the gun as much as you like. IF these guns are not converted like this or to a pump gun the receivers will get so chewed up they will jam up permanently and a gunsmith will have to free them up and convert them or declare them junk.
There was a gun back in the early 1900s that was one of the first semi auto's made in the US it was called the Standard Arms Model G that was a semi auto but had a gas shut off valve and then you could use the gun as a pump. If you did not want to use the gun as a straight pull you could make a forearm to fit the action at the end of the slide and block the gas port and use it as a pump easy enough leaving the spring in place and just doing with what you have here. I preferred to use the original forearm and just make mine straight pull. Yes this does work I already test fired it.
If you take the magazine out and work the bolt you will notice the bolt has to move back about a half an inch for the bolt head to start turning and move the locking lugs out of battery. If the slides do not move either by gas pressure or manual movement the gun will not go out of battery and act like a single shot. Working the slides by either the bolt handle or the block up where the slides end where the gas port is like a pump to manually co-ck the gun then cycles the action.
Just something to think about as if you fire these long enough in the semi auto mode the receivers will go bad this is a given. Remington said 1000 rounds if that which is NOT MUCH. My gunsmith said less rounds than that.
I did this to a 1964 vintage 742 that was given to me by a friend it had no magazine and I told him I would buy it but they have problems with the receivers wearing out so he gave it to me. I now figure I can continue to shoot it and not worry about the receiver wearing out as the 760 pump is basically the same gun only a manual operated pump and their receivers last almost forever as they do not have the lugs bashing the back of the receivers from the pounding of the semi auto action. If you have a 740 or 742 look in the slot where the bolt handle slides in the back of the receiver or look back there with the mag out. Any guns that have been shot even moderately will show a scalloped area on the rails of the receiver where the bolt lugs have been battering the rails. These get bad enough and the bolt will lock up tightly and the gun will them be considered a basket case. Catching it before it gets that far and making it a pump or a straight pull action is the best way to go. If the gun is starting to jam it could be on its way out already.
Pic of the gas port and part of the block I was talking about. This is NOT my gun but a pic I found on the net from Wisners. showing how these guns can rust in wetter climates but it does show part of the gas port and block and the slide action of the semi auto system.
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Originally Posted by Three44s
